Follicle-stimulating hormone (FSH) is important for gametogenesis and gonadal steroid biosynthesis in both males and females. The hormonal regulation of FSH biosynthesis is complex and at present, is poorly understood. In addition to gonadotropin- releasing hormone (GnRH) and gonadal steroids, several recently characterized hypothalamic (GnRH-associated peptide) and gonadal peptides (Inhibins A and B, FSH-releasing peptide) have been shown to be potent regulatory factors for FSH secretion. This proposal focuses on the regulation of human FSH alpha and beta subunit biosynthesis at the level of gene expression. To complement studies of the previously isolated alpha-gene, the human FSHbeta gene and a heterogenous group of FSHbeta cDNAs will be isolated and characterized. Initial studies will use deletion mutagenesis and analyses of expression in transfected cell lines to define the structural features of the alpha and FSHbeta genes that confer cell-specific expression and hormone responsivity. In parallel, interactions between putative gene regulatory elements and intracellular trans-acting factors will be assessed by (1) cotransfection competition assays for binding of intracellular activators or repressors of gene expression by putative regulatory sequences, and (2) analysis of in vitro binding of nuclear proteins to regulatory sequences using gel retardation assays and DNase 1 footprinting studies. These studies will allow detailed analyses of the regulatory regions of the alpha and FSHbeta genes and initial characterization of the intracellular factors that interact with these regulatory elements.